Wise Water Usage, Treatment and Reclamation

With potable water prices going up, and water treatment costs going up even faster, processors are looking at pre-treating or completely treating their own wastewater for reuse.

Finlays Tea installed a Russell Finex liquids solid separator that separates soft and fibrous solids from its wastewater, decreasing BOD levels and allowing some of the treated water to be reused before sending it to the POTW. Source: Russell Finex.

While the food and beverage industry is not the nation’s largest consumer of water, it has to compete with the thermo-electric power industry and farmland irrigation, which according to the US Geological Survey use 52% of the country’s fresh surface water and 42% of ground water, respectively. Irrigated acreage more than doubled between 1950 and 1980, then remained constant before increasing nearly 7 percent between 1995 and 2000. While these numbers seem nebulous, forecasts are not good.

According to government estimates, more than two-thirds of US states will face water shortages within five years because of a combination of rising temperatures, drought, population growth, urban sprawl, waste and excess.

With California facing serious water shortages and other geographical areas seeing abrupt changes in water availability, food and beverage processors have had to rethink their water usage, wastewater treatment and reuse procedures. According to David Jechura, manager of SSOE’s chemical process department, (energy, glass, chemical manufacturing division), most food and beverage plants depend on a potable water supply that meets EPA standards for human consumption. The challenges will be obtaining water of that quality at a reasonable cost, substituting water of lesser quality where possible and treating wastewater as a resource to be used for “water of lesser quality” needs.

For beverage manufacturers, water availability and quality issues are major concerns, according to David Bridgers, Siemens Water Technologies food and beverage development manager. Where water is plentiful for use as an ingredient, it may not be suitable if only standard filtration techniques are employed. In India, for example, there was a very public controversy-and perhaps a perception-about pharmaceuticals and antibiotics getting into and passing through the public water treatment facilities. To address this problem, the major soda bottlers doubled the amount of carbon filtration to clean the water. Membrane filtration is also another alternative to safeguard against undesirable contaminants in source water, says Bridgers. Although the cost of water is relatively low right now, even for beverage companies, this could change depending on location and the amount of treating required before water can be used as an ingredient.

In some areas, the availability of water is enough of an issue that public authorities will allow processors to use water from public supplies, but will strongly encourage processors to minimize the water they use and recycle the water whenever possible, says Brian Heimbigner, Siemens Water product manager, industrial water recycle/reuse. Water shortage in some international locations has become so serious that plants have had to relocate to areas where water was more plentiful.

The drought had been so bad in Atlanta for a couple of years that the city of Atlanta told major water users that they had to reduce their water consumption by 10%, says Bridgers. One soft drink company actually decided to move some of its diet soda syrup production out of the Atlanta area because the diet version uses more water than the regular versions.

Besides shortages, processors are also facing regulatory compliance issues and sustainability efforts, says Richard Molongoski, vice president of CDM, an engineering, construction and consulting firm. Processors are concerned with water foot printing and the public perception of it, regulatory compliance with respect to wastewater discharges, costs of treatment and residuals management. The marketing and “greening” of products (i.e. less water, energy and carbon) and sustainability goals are now key issues, especially in the eyes of customers.

For image-conscious processors, LEED for both new construction and existing buildings offers several opportunities to earn credits for water sustainability, says Darryl Wernimont, Haskell director. “Sustainable Sites” provides the opportunity to earn two points for storm water design; “Water Efficiency” allows for 10 points for innovative wastewater and water reduction, plus water-efficient landscaping; and “Innovation in Design” provides for additional points to be earned, says Wernimont.

Kraft Foods’ Port Melbourne, Australia plant partners with a road construction group to reuse approximately 10 million liters of water for road compaction and dust suppression. Source: Kraft Foods.

New facility or retrofit? Benefits to both

Food and beverage processors typically have wastewater with biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS) and fats/oils/greases (FOG) components, which vary according to products and processes. In most cases, the cleaner the effluent sent to the publicly-owned treatment works (POTW), the lower the processor’s monthly bill will be since most wastewater treatment facilities charge per gallon or weight of water. They may add a surcharge depending on how much the water has to be cleaned to meet regulatory guidelines.

Retrofitting an older facility or building a new plant with wastewater treatment built into the design is a luxury some processors just don’t have. According to Heimbigner, if a processor is facing an edict from the POTW that it will raise the surcharges drastically for sending untreated or poorly treated wastewater, the food manufacturer will quickly discover that it may be less expensive to put in a pre-treatment system than face the surcharges-whether it retrofits or builds new.

According to Mark Hoffman, SSOE project manager, it’s usually more expensive to retrofit than provide treatment in a new installation. It’s difficult to quantify as facilities are unique, although some retrofits could be 20% more expensive than a planned system in a new facility.

“It is certainly logical that starting from scratch and designing a facility with wastewater treatment as part of the plant can make the process more efficient and in some sense more cost effective,” says World Water Works President Mark Fosshage. “However, that luxury is often not available,” he adds. One of the biggest cost differences is found when domestic waste is combined with the manufacturing wastewater system. This limits solids handling options or forces re-piping to separate the two waste streams.

When Mariani Packing Company, located in Vacaville, CA, lost its public treatment plant, it invested in a pre-treatment plant on-site built by Siemens Water that connects to an alternate public wastewater treatment facility in Elmira, CA. The on-site plant handles input BOD levels from 8,000 to 10,000 ppm and cleans to less than 10 ppm. TSS is reduced from 1,500-3,000 ppm to less than 10 ppm. Source: Siemens Water.

Updating technology

Many existing systems are in dire need of updates. “In many food plants, an equalization (EQ) tank followed by neutralization and discharge to the sewerage authority is the wastewater treatment system,” says Henri Asbell, Garratt-Callahan Company wastewater products manager. Many of these plants are being asked or required to treat their wastewater to a higher degree than was formerly practiced, Asbell adds. Frequently one of the new, more efficient dissolved air flotation devices (DAFs) coupled with micro aeration and chemical treatment can remove enough TSS, BOD and FOG so that the wastewater operation will meet permit requirements.

One of these newer primary water treatment systems “reverses the process,” as Ray Guthrie, Clean Water Technology project manager describes. The supplier’s gas-energy mixing (GEM) system first dissolves air into 100% of the waste stream hydro-cyclone mixing heads and uses a floc-seeding aeration technique unlike a traditional DAF system, which uses a floc-collision method. Using this technology, the unit is able to effectively entrain air into the floc as it is being formed, allowing the flocs to float independently, says Guthrie. “This change in theory allows us to obtain much drier sludge, use less chemicals, obtain cleaner water and have a much smaller footprint. We essentially obsolete and replace DAF units,” adds Guthrie.

As a replacement to an existing treatment system in the Midwest, a GEM system coupled with chemicals from Nalco allowed optimized solids recovery at a food processor whose waste stream was 100,000 gallons per day. Overall, sludge solids level improved from less than 1% to more than 27% solids by weight, as well as resulting in a 25% improvement in turbidity, TSS and COD of plant effluent versus the previous treatment protocol. FOG removal was almost 100%, meeting POTW limits and resulting in plant savings of more than $100,000 annually.

Another method of cutting BOD/FOG levels is to pretreat the wastewater using the same biological process used at the POTW, and that is to introduce bacteria to consume the organics as far upstream as possible, says Glenn Cramer, ECOBionics technical advisor for Bio-Amp applications in the food and beverage industry. Typically a processor will run its wastewater through a screening process, pH adjustment, a grease trap and an EQ tank to balance the flow to the utility. If the waste stream’s BOD is still too high because of dissolved organics, continuously introducing bacteria to the stream at least four hours prior to leaving for the POTW can, on average, reduce BOD levels by 35%.

Other, newer treatment methods may include membrane process such as ultrafiltration for oils, membrane bioreactors (MBRs) for removing BOD, and ultraviolet light or ozone for disinfection, says Jechura. Reverse osmosis (RO) membrane treatment usually works best for removing dissolved solids if suspended solids, as measured by a silt density index test, are low enough that the residual suspended solids do not plug the RO membrane pores.

“Using MBR technology is becoming more common to resolve wastewater discharge issues,” says Fred Liberatore, GE Water global director, process separation. “Using electrodialysis reversal (EDR) to reclaim MBR effluent is an interesting trend,” he adds. The EDR is a lower cost solution then RO and it provides benefits like lower fouling, less energy to operate, and chlorine-tolerant membrane. It also provides the processor the ability to do a partial TDS removal versus using RO and removing all the salts. This provides a manufacturer the option to improve overall recovery and reclaim wastewater from food plants for reuse or irrigation. “We are also seeing sporadic movement in the industry to use evaporators and provide zero liquid discharge solutions but this is not as common,” says Liberatore.

Cavendish Farms not only processes and reuses its wastewater, it also converts the solids matter into biogas for fueling its boilers, reducing fossil fuels dependence. Source: Cavendish Farms.

What are acceptable levels?

Pinning specific, hard and fast, numbers to what are acceptable levels of contamination accepted by POTWs is difficult because the levels vary widely from locality to locality and depend upon several factors set by local, state and federal regulations, and how the POTW monitors its own capacity. Hoffman has seen acceptable BOD levels range from 200 mg/l (ppm) to 2,000 mg/l and FOG levels from 5 to more than 100 mg/l.

Fosshage finds that typical averages tend to be 200-300 ppm for TSS, 200-250 ppm for BOD and about 100 ppm for FOG levels. For those POTWs that have been lax on leveling surcharges, processors need to be ready. Due to the forecasted water shortages, lack of fresh water and ever increasing costs to municipalities, it will not be long before all municipalities take another look at costs and pass them on. “A food plant that is not currently faced with treatment requirements or surcharges would be very wise to budget for the possibility in the future,” says Fosshage.

This apple co-op provides 24,000 tons of apples per year to wholesalers and grocery stores, and uses a Pall Aria AP /4/28 membrane filtration system and PVDF hollow fiber microfiltration to clean the suspended contaminants from the water, making it possible to reuse the water for washing. Source: Pall Corp.

Working with the POTW

The relationship between processor and POTW is often symbiotic; they need each other. One of the drawing cards to FAGE locating its new yogurt plant in Johnstown, NY was an underutilized POTW.

After all, “the [public] treatment plant needs a certain amount of BOD to keep its bugs happy,” says Bridgers. He relates instances where soft drink plants decided to build their own treatment facilities so they wouldn’t have to pay additional surcharges. When the POTW heard about it, it told the bottler it was time to talk.

According to Rachel Leary, Dennis Group project engineer, there are some areas where the POTW surcharges are so cheap it doesn’t make any sense to pre-treat wastewater. But many cities and counties can’t pick up the tab like they used to and are increasing their surcharges. When faced with a potential decision to build a pre-treatment system, processors will find that experienced wastewater engineers can help them make a breaking-point calculation, says Leary.

If the public facilities have the capacity, they will take the untreated effluent and surcharge the food plant, as this can be a major source of revenue, says Molongoski. The permit issued by the municipality would normally establish upper limits on flow and loadings as well as the pH range. Municipalities can also use surcharge revenues to help offset the costs of treating the waste produced by the populace.

Municipal industrial waste control officers generally work with food plants to establish discharge limits both can live with, says Asbell. Occasionally, sewer discharge becomes too much to pay and onsite wastewater plant improvements become attractive.

Any good POTW manager knows the cost to treat wastewater based on a pound of BOD or amount of FOG removed, says Jechura. Any good utilities manager or food processor knows the costs associated with removing the same quantities from the plant wastewater. It becomes a matter of negotiation from this point, he adds.

By pumping 248 trillion BOD-consuming bacteria into its pH neutralization tank using ECOBionics’ BioAmp technology, a sauces, dressings and beverage manufacturer reduced its mean BOD levels by 42%, and variability declined by 65%, saving the processor $175,000 per year in surcharges. Source: NCH Corp.

Reuse-is it cost effective?

Ideally, reducing the water leaving the plant can mean lower surcharges at the utility, says Leary. Instead, it may make sense to clean the water and reuse it internally, possibly in heat exchanger systems, cooling towers, wet scrubbers or for washing trucks. Kraft Foods Australia in Port Melbourne partnered with a road construction group to reuse approximately 10 million liters of water per year for road compaction and dust suppression. In Germany, Kraft reduced water usage by 7% (18.5 million gallons) per year by reusing water to run its cheese plant’s cooling towers. In Jacksonville, FL, Kraft installed a closed-loop system to reuse water to cool coffee-grinding equipment, saving 20 million gallons.

Extensive treatment for process wastewater is required for most reuse applications, says Molongoski. If a plant has a pretreatment plan to meet ‘higher’ discharge limits of a POTW (say 300 mg/l BOD/TSS), this treatment would not produce an effluent of the quality needed for reuse. If it has a direct discharge treatment plant that meets more stringent discharge requirements (20 mg/l BOD/TSS), then reuse water quality may be achievable with additional treatment such as filtration or membrane treatment.

Processors must weigh how much sense it makes to reuse water in terms of the costs. “When the cost of water is above $1.5/1,000 gallons, I can successfully show water savings projects with ROIs of 2.5 years or less,” says Mike Eschenbrenner, SSOE senior mechanical designer. Process water is usually a bad choice for reused water, but cooling tower make-up and closed-loop cooling applications are the easiest to incorporate in savings initiatives. CIP final rinse water can usually be used without any treatment for cooling tower make-up, and sometimes boiler feed.

Fosshage thinks water and sewer costs have to be more than $3-5/1,000 gallons to warrant reuse of water within the plant. When there is a short supply of water, reuse makes even more sense. World Water Works was part of a project in a poultry plant where approximately 50% of the water is returned for direct food contact. USDA guidelines must be met in this case. Beyond process use, a boiler is a popular application for reusing water, but TDS concentrations are often a concern, says Fosshage.

For boilers, water quality must be reasonably good, says Michael Scholnick, Garratt-Callahan senior product manager and boiler products manager. Typically, contaminants and foulants are not acceptable in waters used as boiler makeup, and acceptable published limits for boiler feedwaters exist that relate to the operating pressure of the boiler. Polishers, softeners, and RO units can provide the necessary cleaning to condition reuse water. Boiler blowdown water can be captured and reused with the proper equipment, and steam condensate is typically captured and returned, Scholnick adds. Boiler blowdown, with a flash tank, can be captured, cooled, polished, and then most likely sent to RO for reuse. However, the cost and energy required to reuse could easily outweigh the benefits.

Cooling tower water should primarily be free of suspended solids and organic contaminants as these affect corrosion and biological control issues, says Ernie Appelhans, cooling water products manager, Garratt-Callahan. High levels of inorganic constituents can place limits on cycles of concentration that impact scale, corrosion, and restrict the materials of construction within the recirculating cooling system. Depending on the quality of the wastewater, and how it would affect reuse, cleanup can be filtration, lime softening, ultra/nano-filtration, RO, MBR systems, or activated carbon, among others.

For Finlays, one of the world’s largest tea companies, surcharges from the local wastewater utility were increasing, making it necessary for it to cut the level of BOD in its waste stream. After considering several technologies, it settled on a liquid solid separator from Russell Finex. The device is a multi-purpose unit that separates soft and fibrous solids from liquids handling particles to 25 microns and up to 15,000 gallons per hour.

“Removing a larger percentage of solids from our waste water has allowed Finlays to contribute to a cleaner environment as well as reduce our costs for disposing waste to local landfills,” says Malcom Eade, Finlays plant manager. “By minimizing penalty fines for high BOD levels, we are confident we will see a return on investment within six months of installation.” Finlays has another green benefit from the installation. It reuses wastewater and pumps it back into its manufacturing process, reducing the use of additional town water for the decaffeination process. “Due to the liquid solid separator, we are recycling water which is better for the environment, and we also foresee a significant reduction in water charges,” says Eade.

Poultry processing is notorious for its use of water. At a processing plant located in Batesville, AR, a water reuse system was designed to treat up to two-million gallons per day. The system treats all plant effluent of about 1.5 million gallons per day. Approximately 700,000 gallons of the water, which meets all USDA guidelines for poultry water reuse, is made available to the kill facility daily. The collective team of World Water Works, Zentox Corp., Install Inc., and FTN Associates added a new EQ tank with mixing, upgraded the existing DAF with a Nikuni pump to improve performance and consistency, installed a two-stage moving bed biofilm reactor (MBBR) to remove soluble BOD, and designed a resource DAF to remove the biomass from the MBBR. With influent BODs of 6,000 ppm and effluents of 5 ppm, influent TSS of 4,125 ppm and effluents of 4 ppm, and influent FOG of 366 and effluents of 1 ppm, the quality may suffice for direct discharge, though currently it is sent to the local treatment facility.

Treatment provides other benefits

For some processors with enough BOD and continuous flow, there are other benefits in setting up a treatment plant on site. According to Staffan Akerstrom, EPS Corp. chief operating officer, “Through the use of biodigesters, we’ve been able to create methane gas to fire generators and boilers. The result is multi-beneficial for the processor. By treating their own wastewater, we’ve enabled them to cut energy expenditures, reduce costs associated with having the municipality treat the wastewater and help them move toward more sustainable manufacturing practices.”

Biogas is not for every plant. For plants using anaerobic digesters to generate methane, a high-strength organic wastewater will be required with at least or more than 2,000 mg/l BOD, says Molongoski. The digesters can also handle sludge and inedible wastes, and leftover solids can usually be used for animal feed, compost or energy production through burning it.

Sierra Nevada Brewing Company built an on-site water treatment system, which includes an anaerobic digester backed up by an aerobic system. The brewer now uses the resultant methane gas to power the boilers in its plant.

Another high-strength application capable of supporting a biogas facility is Cavendish Farms, one of North America’s leading producers of frozen potato products, located in Prince Edward Island, Canada. Solids are separated from the wastewater and sent to an anaerobic digester. The company saves 10 million liters of fossil fuel in powering its boilers by the gas generated from the potato sludge. After the sludge is spent in the bioreactor, it is then converted to an organic fertilizer.

Norit Haffmans successfully tested its first biogas upgrading plant where green gas (upgraded methane to meet natural gas specifications with a membrane separation unit) and liquid carbon dioxide is being produced from the biogas, says Dan Gruber, Norit Haffmans technical manager, CO2 systems. The biogas produced from the wastewater treatment systems is about half methane and half carbon-dioxide. The upgraded methane can be used as a fuel in existing process equipment or sold to the gas grid. The CO2 is upgraded to food-quality and can be used to adjust the pH of wastewater or carbonization of beer and beverages.

Whether or not it’s cool to be green, pre-treating and reusing water may be the ticket processors need to keep some of their budget for other purposes-such as new packaging machinery or track-and-trace software. At the same time, communities and customers respect processors who are making an effort to be sustainable and assume their responsibility as good stewards of the environment.

Wayne Labs has more than 20 years of editorial experience in industrial automation. He served as senior technical editor for I&CS/Control Solutions magazine for 18 years where he covered software, control system hardware and sensors/transmitters. Labs ran his own consulting business and contributed feature articles to Electronic Design, Control, Control Design, Industrial Networking and Food Engineering magazines. Before joining Food Engineering, he served as a senior technical editor for Omega Engineering Inc. Labs also worked in wireless systems and served as a field engineer for GE’s Mobile Communications Division and as a systems engineer for Bucks County Emergency Services. In addition to writing technical feature articles, Wayne covers FE’s Engineering R&D section.